Public court documents identified the off-duty officer as Fred Klein, 39. Authorities say he sustained a cut over his left eye that required stitches to close, ligament damage in one arm, and back pain, after three men set upon him with a baseball bat Saturday, according to authorities.

The violent episode happened shortly after 2 a.m., while one of Klein's young neighbors was throwing a house party, according to police.

The three alleged assailants -- Matthew Catanese, 20, of the 200 block of Monahan Avenue, New Springville; John T. Lafrancesca, 20, of Bradley Avenue, Meiers Corners; and Wayne Laborante, 19, of Adam Court, New Springville -- showed up at the party uninvited and were kicked out, said NYPD spokesman Det. Joseph Cavitolo.

So they took to roaming the neighborhood, loudly, and Klein's father told them through his window to quiet down, Cavitolo said.

When the men started beating on his father, Klein's mother woke him up, and the officer came out, identifying himself as police, Cavitolo said. Klein is assigned to the North Shore's 120 Precinct.

The men then ganged up on Klein, authorities said, punching him in the face and body, and hitting him with a baseball bat.

Police arrived on the scene and arrested Catanese and Lafrancesca. They caught up with Laborante later that day.

Mark Fonte, Lafrancesca's lawyer, tells a different version of events.

Lafrancesca was leaving the party -- he wasn't kicked out -- with a female friend when he spotted "some monster-looking guy, apparently the off-duty cop, pounding on some guy," who turned out to be Catanese, Fonte said.

Lafrancesca got out of his car to try to stop the fight, Fonte said.

"He didn't even get a chance to break it up before the uniformed officers were on the scene," Fonte said. "He was not a part of the fight. He was not involved in the fight... He merely witnessed his friend being beaten by the off-duty cop."

Catanese presented his bruises to a Stapleton Criminal Court judge at the men's arraignment yesterday, Fonte said, adding that Lafrancesca's female friend can verify his side of the story.

All three face felony and misdemeanor assault charges misdemeanor weapon charges. Laborante, who police say was carrying pot and Xanax at the time of his arrest, also faces misdemeanor drug charges.

Laborante remains locked up on $2,500 bail, while Catanese and Lafrancesca have both been released on $1,000 bail.